Polyphenyl thioether lubricating compositions

ABSTRACT

Lubricating compositions comprising polyphenyl thioethers, polyphenyl ethers-thioethers or mixtures thereof and containing small amounts of a polar organic compound and an organic phosphinic acid or ester have improved lubricating properties. These compositions are useful as lubricants over wide temperature ranges.

ited States Patent [1 1 Clark Oct. 29, 1974 [54] POLYPHENYL THIOETHER LUBRICATING COMPOSITIONS [75] Inventor: Frank S. Clark, St. Louis, Mo. [73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed:. Feb. 5, 1973v [21] ApplpNo; 329,796

Related U.S. Application Data- [62] Division of Ser. No. 102,969,.Dec. 30, 1970, Pat. No.

[52] U.S. Cl..; 252/46.7, 252/49.8, 252/57, 252/46.6

[51] Int. Cl. C10m l/48 ClOm 1/24 [58] Field of Search 252/46.6, 46.7, 49.8, 56 R, 252/57 [56] References Cited UNITED STATES PATENTS 2,174,019 9/1939 Sullivan 252/49.8

Primary ExaminerW. Cannon Attorney, Agent, or FirmRobert E. Wexler 57 ABSTRACT Lubricating compositions comprising polyphenyl thioethers, polyphenyl ethers-thioethers or mixtures thereof and Containing small amounts of a polar organic compound and an organic phosphinic acid or ester have improved lubricating properties. These compositions are useful as lubricants over wide temp'erature ranges.

2 Claims, N0 Drawings POLYPHENYL THIOETHER LUBRICATING COMPOSITIONS This is a division of application Ser. No. 102,969, filed Dec. 30, 1970, now US. Pat. No. 3,748,269 dated July 24, 1973.

This invention relates to improved lubricating compositions comprising polyphenyl thioethers, mixed polyphenyl ethers-thioethers and mixtures thereof, containing from three to eight aromatic groups and a small amount of a polar organic compound and an organic phosphinic acid as lubricating additives.

Polyphenyl thioethers and polyphenyl etherthioether combinations have found wide application as functional fluids due to their excellent thermal stability and lubricity. For example they have been found to be valuable as hydraulic fluids and as lubricants in motor operation, particularly in jet engines.

Development of synthetic base stocks such as the polyphenyl thioether has provided lubricant fluids which are useful at elevated temperature such as 400 to 500F. [t is known that one of the aspects in which the polyphenyl thioether base stocks are considered deficient in their lubricating characteristics, especially for steel on steel or on chrome anodized aluminum. These lubricating characteristics include the load-carrying abilities and wear properties, especially under conditions of pumping the lubricant where the pump contains a chrome anodized aluminum bearing surface or gear box. Thus there is a demand for additives for polyphenyl thioethers which additives will improve the lubricity of the polyphenyl thioethers for steel on steel or on chrome anodized aluminum surfaces.

Anobject of the present invention is to provide-for improved lubricating compositions employing polyphenyl thioethers, polyphenyl ether-thioethers, or mixtures thereof as base stocks for applications where at least one of the surfaces to be lubricated is chrome anodized aluminum.

These and other objects will become evident upon consideration of the following specification and examples.

it has now been found that compositions consisting essentially ofa major amount of a polyphenyl thioether base fluid having the formula Ys is sulfur and n is an integer having a value of from 1 to 6 and an additive amount of a polarorganic com-' pound andan organic phosphinic acid have unusual ability to lubricate steel on chrome anodized aluminum and steel on steel.

The amount of the polar organic compound employed in the compositions of this invention can range from 0.01 to about 0.5 percent by weight. It is pre- 2 ferred to employ the polar organic compound in the compositions of this invention in amounts of from 0.04 to 0.15 percent by weight based upon the total composition.

The amount of the organic phosphinic acid or ester employed in the compositions of this invention is from about 0.05 to about 1.0 percent by weight of the total composition. It is preferred to employ the organic phosphinic acid or ester in the compositions of this invention in amounts of from about 0.070 to about 0.2 percent by weight of the total composition.

The improvement in lubricity characteristics achieved by the addition of a perfluoro dibasic acid as the polar organic compound and the organic phosphinic acid or ester to the polyphenyl thioether base fluid is particularly unusual and surprising. Wear on a chrome anodized aluminum bearing surface is decreased at test temperatures of 200F. whereas when the base fluid is tested without the additive the lubricity wherein n is an integer of from 1 to 8. it is particularly preferred to employ perfluorinated dibasic acid of formula ll wherein n is an integer of from 2 to 6.

Illustrative of the carboxy substituted polyphenyl thioethers which are employed in the compositions of this invention are those having the formula wherein R, R, Y and'n are as above-defined with the proviso that at least one Y is sulfur and that from one to two of R and R is substituted with a carboxy group and x is an integer of l or 2. Such carboxy substituted polyphenyl thioethers are for example m-(mphenylmercaptophenylmercapto)benzoic acid, m-(phenylmercapto)benzoic acid, o-(mphenylmercaptophenylmercapto)benzoic acid and the other carboxy substituted polyphenyl thioethers.

Illustrative of the substituted phenols which are useful in the compositions of this invention are the 2,6-(al-' kyl) phenols such as for example 2,6-di-t-butyl-4- methyl phenol and the like. It is preferred that the alkyl groups on the phenol contain from one to 12 carbon atoms.

illustrative of the aryl substituted fatty acids which are useful in the compositions of this invention are those havingthe general formula I ArC,,H ,,COOH wherein'Ar is an aryl group containing from six to 16 carbon atoms and a is an integer of from 8to 24. Illustrative of these aryl substituted fatty acids areyfor example, phenyloctadecanoic acid, phenyloctanoic acid, tolyldodecanoic acid, xylyltetracosanoic acid and the like.

Illustrative of the acetylenic dibasic acids useful in the compositions of this inventionare those having the general formula where b and c are integers of from O to l inclusive. Acetylene dicarboxylic acid is especially preferred for use in the compositions of this invention.

Illustrative of the aryl phosphate esters useful in the compositions of this invention are those having the formula wherein R is an aryl group containing from six to 16 carbon atoms and R and R are alkyl groups containing from one to 12 carbon atoms or an R group. It is preferred that when R, R and R all represent aryl groups that at least one of the aryl groups be an alkyl substituted aryl group. Illustrative of the phosphate esters are for example, tricresyl phosphate, dibutyl phe nyl phosphate, cresyl diphenyl phosphate, xylyl dicresyl phosphate, cresyl dioctyl phosphate and the like.

Illustrative of the perfluorinated dibasic acids represented by formula II are, for example, perfluoro malonic acid, perfluoro succinic acid, perfluoro azelaic acid and perfluoro sebacic acid.

The organic phosphinic acids or esters which are employed in the compositions of this invention are those of the formula wherein R" is an aryl group containing from six to 16 carbon atoms, a halogenated aryl group or an alkyl group containing from one to l2'carbon atoms, and R' is hydrogen or an R" group. Illustrative of the groups represented by R" and R"' are, for example, phenyl, tolyl, xylyl, naphthyl, a-methyl-naphthyl and diphenyl, and such aryl groups substituted with halogen or with alkyl groups containing up to carbon atoms. Further alkyl substituted aryl groups are nonylphenyl, ethylphenyl. butylphenyl, t-butylphenyl and the like. such halogen substituted aryl groups are pchlorophenyl, o-bromophenyl. m-fluorophenyl, piodophenyl. chlorotolyl, bromoxylyl, chloronaphthyl, and the like. Illustrative of the alkyl groups represented by R" and R are, for example, methyl, ethyl, propyl, isobutyl, pentyl, t-butyl, hexyl, isooctyl, nonyl, decyl, dodecyl, and the like. Such aryl phosphinic acids are, for example, phenylphosphinic acid, nonylphenylphosphinic acid, tolylphosphinic acid, xylylphosphinic acid, naphthylphosphinic acid, diphenylphosphinic acid and the like. It is especially preferred to employ in the compositions of this invention compounds of formula III wherein R" is an aryl group and R is hydrogen.

The polyphenyl thioethers employed in the composition of this invention have from three to eight benzene rings and from one to seven sulfur atoms with the sulfur atoms joining the benzene rings in chains as ether linka es.

By the term polyphenyl thioether as used herein is meant a compound or physical mixture of compounds represented by formula I. The term includes compounds wherein all of the Ys in formula I are sulfur. The term also includes those compounds which contain both oxygen and sulfur linkages between the benzene rings.

The compositions of this invention contain a major amount of the polyphenyl thioether base stock, i.e., at least 50 percent by weight of the total composition comprises a polyphenyl thioether. It is preferred that at least percent by weight of the composition be a polyphenyl thioether base stock and even more preferred that at least percent by weight of the total composition comprise a polyphenyl thioether.

The compositions of this invention can also contain from 0.01 to 10 percent by weight of the total composition of a dialkyl hydrogen phosphite extreme pressure additive. The dialkyl hydrogen phosphites useful are those wherein the alkyl groups contain from one to 12 carbon atoms. These alkyl groups are for example, methyl, ethyl, propyl, isopropyl, butyl, secbutyl, tbutyl, hexyl, decyl, isodecyl, dodecyl and the like.

Illustrative of the alkyl-substituents present in the phenyl and phenylene groups of the polyphenyl thioethers are for example, methyl, ethyl, propyl, butyl and the like. Illustrative of the alkoxy-substituents are, for example, methoxy, ethoxy, propoxy, butoxy and their isomers.

Illustrative of the polyphenyl thioethers which can be employed as base stocks for the compositions of this invention are the bis(phenylmercapto)benzenes. For example bis(m-phenylmercapto)benzene bis(o-phenylmercapto)benzene bis(p-phenylmercapto)benzene bis(m-phenylmercaptophenyl)sulfide bis(o-phenylmercaptophenyl)sulfide bis(p-phenylmercaptophenyl)sulfide (m-phenylmercaptophenyl) (o-phenylmercaptophenyl)sulfide p-phenylmercapto-m'-phenylmercapto diphenyl sulfide o-bis(o-phenylmercaptophenylmercapto)benzene p-bis(p-phenylmercaptophenylmercapto)benzene p-bis(o-phenylmercaptophenylmercapto)benzene p-bis(m-phenylmercaptophenylmercapto)benzene m-bis(p-phenylmercaptophenylmercapto)benzene o-bis(p-phenylmercaptophenylmercapto)benzene and the like and mixtures thereof.

Illustrative of the mixed polyphenyl ether-thioether compounds which can be employed as base stocks in the compositions of this invention are for example,

o-phenylmercapto-m-phenoxy benzene p-phenylmercapto-o-phenoxy benzene m-phenoxy-p-phenylmercapto benzene o-phenylmercapto-p'-phenoxydiphenyl sulfide o-phenylmercapto-m-phenoxydiphenyl sulfide o-phenoxy-m'-phenylmercaptodiphenyl sulfide m-phenoxy-p-phenylmercaptodiphenyl sulfide o-phenoxy-p-phenylmercaptodiphenyl sulfide p-phenoxy-p-phenylmercaptodiphenyl sulfide o-phenoxy-o-phenylmercaptodiphenyl sulfide 6 4,4'-bis(m-trifluorornethylphenylmercapto )diphenyl ether 3,4-bis(m-trifluoromethylphenylmercapto)diphenyl o,o'-bis(phenylmercapto)diphenyl ether ether o-phenylmercapto-m-phenylmercaptodiphenyl ether 5 2,3'-bis(m-trifluoromethylphenylmercapto)diphenyl o-phenylmercapto-p-phenylmercaptodiphenyl ether ether m-(m-phenylmercaptophenylmercapto) (m- 3,3-bis(p-trifluoromethylphenylmercapto)diphenyl phenoxyphenylmercapto)benzene ether [m-( m-phenylmercaptophenylmercapto)phenyl] [m- 3,3-bis(o-trifluoromethylphenylmercapto )diphenyl (m-phenoxyphenylmercapto)phenyl]sulfide l0 ether 3-(m-phenylmercaptophenylmercapto)-3-(m- 3,3-bis(m-methoxyphenylmercapto)diphenyl ether phenylmercaptophenoxy)diphenyl sulfide 3,4'-bis(m-isopropoxyphenylmercapto)diphenyl 3 ,3 '-bis( m-phenylmercaptophenylmercapto )dipheether nyl ether 3,4-bis(m-perfluorobutylphenylmercapto)diphenyl 3-(m-phenylmercaptophenylmercapto)-3'-(mether phenoxyphenoxy)diphenyl sulfide 2-(m-tolyloxy)-2-phenylmercaptodiphenyl sulfide 4-(m-phenylmercaptophenylmercapto)-4-(m- 2-(p-tolyloxy)-3'-phenylmercaptodiphenyl sulfide phenylmercaptophenoxy)diphenyl ether 2-(o-tolyloxy)-4'-phenylmercaptodiphenyl sulfide 3-( m-phenylmercaptophenylmercapto)-3'-(m- 3-(m-tolyloxy)-3'-phenylmercaptodiphenyl sulfide phenoxyphenylmercapto)diphenyl ether 3-(m-tolyloxy)-4-phenylmercaptodiphenyl sulfide 4,4-bis(m-phenylmercaptophenoxy)diphenyl sulfide 4-(m-tolyloxy)-4Pphenylmercaptodiphenyl sulfide 3-xylyloxy-4'-phenylmercaptodiphenyl sulfide 4,4'-bis( m-phenoxyphenylmercapto)diphenyl sulfide 3-xylyloxy-3'-phenylmercaptodiphenyl sulfide 3-phenoxy-3-(m-tolylmercapto)diphenyl sulfide 3-(m-phenoxyphenylmercapto)-3'-(m- 3-phenoxy-4'-(m-tolylmercapto)diphenyl sulfide phenylmercapto phenoxy)diphenyl sulfide 2-phenoxy-3-(p-tolylmercapto)diphenyl sulfide 3,3'-bis(m-phenylmercaptophenoxy) diphenyl ether 3-phenoxy-4'-(m-isopropylphenylmercapto)diphenyl sulfide v 4-(m-phenylmercaptophenylmercapto)-4'-(m- 3-phenoxy-3'-(m-isopropylphenylmercapto)diphephenoxyphenoxy)diphenyl ether nyl sulfide 3-( p-phenylmercaptophenoxy )-3 p- 3-m-toloxy-3'-( m-isopropylphenylmercapto )diphephenoxyphenoxy) diphenyl sulfide nyl sulfide I 3-(m-phenylmercaptophenoxy)-3-(m- 4-(m-trifluoromethylphenoxy)-4'-phenylmercapphenoxyphenylmercapto)diphenyl ether todiphenyl sulfide 3,3-bis(m-phenoxyphenylmercapto)diphenyl ether 3-(m-trifluoromethylphenoxy)-4'-phenylmercapand todiphenyl sulfide 3-(m-phenoxyphenylmercapto)-3'-(m- 2-(m-trifluoromethylphenoxy)-3'-phenylmercapphenoxyphenoxy) diphenyl sulfide. todiphenyl sulfide in addition to the foregoing compounds, the phenyl 3-(m-trifluoromethylphenoxy)-3-phenylmercapand phenylene groups of such compounds can contain 40 todiphenyl-sulfide substituents, such as alkyl of one to four carbon atoms, 3-(p-chlorophenoxy)-3'-phenylmercaptodiphenyl alkoxy of one to four carbon atoms and halogen such sulfide as chlorine, bromine and fluorine. Examples of such 3-(m-bromophenoxy)-4-phenylmercaptodiphenyl compounds are as follows: sulfide 4.4-bis(m-tolylmercapto)diphenyl ether bis[m-(m-chlorophenoxy)phenyl]sulfide 3,3-bis(m-tolylmercapto)diphenyl ether m-bis[3-(p-methylphenylmercapto)phenoxy]ben- 2,4-bis(m-tolymercapto)diphenyl ether zene 3,4'-bis(m-tolylmercapto)diphenyl ether m-bis[3-(m-trifluoromethylphenoxy)phenylmercap- 3,3'-bis(p-tolylmercapto)diphenyl ether tolbenzene 3,3'-bis(xylylmercapto)diphenyl ether mbis[3-(m-bromophenoxy)phenylmercapto]ben- 4,4-bis(xylylmercapto)diphenyl ether zene 3,4-bis(xylylmercapto)diphenyl ether 3,3-bis[m-(p-methylphenylmercapto)phenoxy]- 3,4'-bis(m-isopropylphenylmercapto)diphenyl ether diphenyl sulfide 3,4'-bis[m-(p-methylphenylmercapto)phenoxy]- 3,3-bis(m-isopropylphenylmercapto)diphenyl ether diphenyl sulfide 3-(p-xenyloxy)-3'-phenylmercapto diphenyl sulfide, 2,4'-bis(m-isopropylphenylmercapto)diphenyl ether and the like and mixtures thereof. It is also contemplated within the scope of this invention to employ mixtures of polyphenyl ether-thioethers as base stocks.

The compositions of this invention are useful as lubricants under extreme conditions. The compositions are especially useful for steel on chrome anodized aluminum lubrication.

' The following examples serve to further illustrate the invention. All parts are parts by weight unless otherwise expressly set forth.

3,4-bis(p-tert-butylphenylmercapto)diphenyl ether 4,4-bis(p-tert-butylphenylmercapto)diphenyl ether 3,3-bis(p-tert-butylphenylmercapto)diphenyl ether 3 ,3 -bis( 2,4-di-tert-butylphenylmercapto)diphenyl ether 3,3 '-bis(3-chlorophenylmercapto)diphenyl ether 4,4-bis( 3-chlorophenylmercapto)diphenyl ether 3,3'-bis(m-trifluoromethylphenylmercapto)diphenyl ether EXAMPLE 1 (507! by weight) H257: by weight) meta-bis(phenylmercapto)benzene bis( phenoxyphenyl )sulfide (phenoxylphenyl) (phenylmercuptophenyl)sulfide bis(phenylmcrcaptophenyl)sulfidc 3 ring and 5 ring thioethers (23.5% by weight) (l2.65'7( by weight) (1.357: by weight) This mixture is stirred for about 12 hours at 40-45C. After cooling to room temperature the mixture is filtered to remove a small amount of insoluble material.

The aluminum lubricity of the composition of Example l was shown using a chrome anodized oil pump. This is a Pratt & Whitney .lT3D-3B main engine pump. This type of pump is commonly used in jet engine gear boxes. The gear box oil pump is a compound pump composed of the pressure oil pump and the gear box scavenge pump operating from a single shaft. Both drive gears of the pumps and the rotating shaft are hung from two outboard journals with a journal in the middle separating the two pumps. Rotating drive for both pumps is provided by a single axially located splined shaft which extends through one side of the pump housing to a power source. The driven or idle mating gears in these pumps rotate on a fixed shaft. The rotating shaft is steel, the case and journals are chrome anodized aluminum. Design loading is 50 psi for the pressure pump.

Normally, the journals are part of the pump case. For testing purposes, the housing is widened and chrome anodized bushings are placed between the shaft and the journal. Lubricity failure results from wear or seizure of the bushings. These are then replaced allowing continual testing with one pump.

A shock cycle test was used to evaluate fluids. The oil was circulated in the pump under no load while being heated to 200F. The output of the pump was throttled until a discharge pressure of 20 psi was reached. This pressure was held for ten seconds, then lowered to psi for seconds. This off-on shock cycle was repeated times at 20 psi, 20 times at psi, psi, psi, psi, and psi. This final load is 50 percent excess load above the design load. Completion of 120 cycles without wear or seizure of the bushings constitutes a successful test.

The composition of Example 1 was able to complete 120 testing cycles without failure of the bushings. The base oil containing 0.1 percent diisopropyl'hydrogen phosphite failed the test after 60 cycles. The base oil with only phenylphosphinic acid (0.l percent) failed at 62 cycles. The thioethers containing only perfluoroglutaric acid (0.08 percent) failed after 84 cycles.

The lubricating ability of the fluids of this invention was shown with a slow speed four ball machine. A slow speed four ball machine measures the boundary lubricity action of additives. This test is a variation of the well known Shell Four Ball Test in which a ball is rotated against three stationary balls. Wear scars and/or seizure loads measure additive lubricity. In the slow speed instrument the three stationary balls are replaced with circular discs. Standard operating conditions are:

3 Kg. load 1 r.p.m.

Room temperature to 700F.

The speed of rotation is very low, namely one r.p.m. This equals 0.88 inches/minute. This is done for two reasons. It insures boundary conditions, i.e., metal to metal contact. it also eliminates metal skin temperature flashes which can occur at high speeds. Thus the bulk oil temperature is equivalent to the metal surface temperature. Under these conditions wear is negligible and friction isused to follow lubrication. After covering the ball and disc with the test oil, the initial friction is recorded. The test sample is then heated to 700F. with continuous recording of the friction. This gives a boundary friction-temperature profile for the experimental fluid over thistemperature range.

From 200 to 700F. the boundary friction on M50 steel for the blend from Example 1 was lower than that of the base stock containing only phenyl phosphinic acid. The friction lowering was greatest above 600F. This temperature range corresponds to the metal skin temperatureof bearing components at high temperature conditions.

EXAMPLE 2 To grams of the base fluid of thioethers from Example was added 0.075 gram phenylphosphinic acid and 0.05 gram of acetylene dicarboxylic acid. After heating at 45C. for about 20 hours, the blend was cooled to room temperature and filtered.

A boundaryfriction-temperature curve for the fluid from Example 2 was run on M50 steel. The boundary friction for the blend was significantly lowered relative to the base stock containing only phenylphosphinic acid over a temperature range of 400 to 700F.

EXAMPLE 3 To 100 grams of the base fluid of the thioethers as set forth in Example 1 was added 0.075 gram phenylphosphinic acid and 0.05 gram of m (mphenylmercaptophenylmercapto)benzoid acid. After heating at 45 for about 20 hours, the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 3 was run on M50 steel. The boundary friction for the blend from 500 to 700F. was significantly lower than a blend containing only phenylphosphinic acid.

EXAMPLE 4 To 100 grams of the base fluid of thioethers from Example l was added 0.075 gram phenylphosphinic acid and 0.05 gram of 2,6-di-t-butyl-4-methyl phenol. After heating at 45C. for about three hours the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 4 was run on M50 steel. The boundary friction for the blend was either significantly lower than, or equal to the boundary friction of the base stock containing only phenylphosphinic acid over a temperature range of from room temperature to 700F. From 500F. to 700F. the boundary friction of the blend of Example 4 was significantly lower than that of the blend containing only phenylphosphinic acid.

EXAMPLE To 100 grams of the base fluid of thioethers from Example l was added 0.075 gram phenylphosphinic acid and 0.05 gram of tricresylphosphate. After heating at 40 to 45C. for about 3 hours the blend was cooled to room temperature and filtered.

A boundary friction-temperature curve for the fluid from Example 5 was run on M50 steel. The boundary friction for the blend was lower than for a base stock containing only the phenylphosphinic acid over a temperature range of from room temperature to 700F.

EXAMPLE 6 To 100 grams of the base fluid of thioethers from Example was added 0.075 gram phenylphosphinic acid and 0.05 gram of phenyloctadecanoic. After heating at 40 to 45C. for about 3 hours the blend was cooled to room temperature.

A boundary friction-temperature curve for the fluid from Example 6 was run on M50 steel. The boundary friction for the blend was lower than for a base stock containing only the phenylphosphinic acid over a temperature range of from 600 to 700F.

It will be appreciated that the composition of the invention, in addition to the polyphenyl thioether base fluid and the organic phosphinic active additive, may also contain other additives, such as oxidation inhibitors, rust and corrosion inhibitors, antifoaming agents, detergents, viscosity index improvers such as polymeric materials for example, polyacrylate alkyl esters, polymethacrylate alkyl esters, polyoxyalkylene compounds, polyurethanes and the like. Such additives are usually employed in amounts as low as 10 parts per million for antifoaming agent to as much as 15 parts by weight of the total compositions for viscosity index improvers.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited thereto and that it can be variously practicedwithin the scope of 40 the following claims.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

l. A lubricant composition consisting essentially of a major amount of a polyphenyl thioether having the formula 1.0 percent by weight of an organic phosphinic acid of the formula wherein R is an aryl group of from six to 16 carbon atoms, a halogen substituted aryl group of from six to 16 carbon atoms, an alkyl substituted aryl group containing from six to 16 carbon atoms or an alkyl group containing one to 12 carbon atoms, R is hydrogen or an R" group and from 0.01 to 0.5 percent by weight of aryl substituted fatty acids of the formula wherein Ar is an aryl group containing from six to 16 carbon atoms and a is an integer of from 8 to 24.

2. A composition of claim 1 wherein the aryl substituted fatty acid is phenyloctadecanoic acid. 

1. A LUBRICANT COMPOSITION CONSISTING ESENTIALLY OF A MAJOR AMOUNT OF A POLYPHENYL THIOETHER HAVING THE FORMULA
 2. A composition of claim 1 wherein the aryl substituted fatty acid is phenyloctadecanoic acid. 